RC matching in a touch screen

ABSTRACT

A touch screen. In some examples, the touch screen can comprise a first element coupled to a first sense connection, and a second element coupled to a second sense connection. In some examples, the first and second sense connections can be configured such that a load presented by the first sense connection and the first element is substantially equal to a load presented by the second sense connection and the second element. In some examples, the first and second sense connections can comprise detour routing configured such that a resistance of the first sense connection is substantially equal to a resistance of the second sense connection. In some examples, the first and second sense connections can be coupled to dummy routing configured such that a first capacitance presented by the first sense connection is substantially equal to a second capacitance presented by the second sense connection.

FIELD OF THE DISCLOSURE

This relates generally to touch sensor panels, and more particularly tobalancing loads presented by connections in a touch screen.

BACKGROUND OF THE DISCLOSURE

Many types of input devices are presently available for performingoperations in a computing system, such as buttons or keys, mice,trackballs, joysticks, touch sensor panels, touch screens and the like.Touch screens, in particular, are becoming increasingly popular becauseof their ease and versatility of operation as well as their decliningprice. Touch screens can include a touch sensor panel, which can be aclear panel with a touch-sensitive surface, and a display device such asa liquid crystal display (LCD) that can be positioned partially or fullybehind the panel so that the touch-sensitive surface can cover at leasta portion of the viewable area of the display device. Touch screens canallow a user to perform various functions by touching the touch sensorpanel using a finger, stylus or other object at a location oftendictated by a user interface (UI) being displayed by the display device.In general, touch screens can recognize a touch and the position of thetouch on the touch sensor panel, and the computing system can theninterpret the touch in accordance with the display appearing at the timeof the touch, and thereafter can perform one or more actions based onthe touch. In the case of some touch sensing systems, a physical touchon the display is not needed to detect a touch. For example, in somecapacitive-type touch sensing systems, fringing electrical fields usedto detect touch can extend beyond the surface of the display, andobjects approaching near the surface may be detected near the surfacewithout actually touching the surface.

Capacitive touch sensor panels can be formed by a matrix ofsubstantially transparent conductive plates made of materials such asIndium Tin Oxide (ITO). It is due in part to their substantialtransparency that capacitive touch sensor panels can be overlaid on adisplay to form a touch screen, as described above. Some touch screenscan be formed by partially integrating touch sensing circuitry into adisplay pixel stackup (i.e., the stacked material layers forming thedisplay pixels).

SUMMARY OF THE DISCLOSURE

Some capacitive touch sensor panels can be formed by a matrix ofsubstantially transparent conductive plates made of materials such asIndium Tin Oxide (ITO), and some touch screens can be formed bypartially integrating touch sensing circuitry into a display pixelstackup (i.e., the stacked material layers forming the display pixels).Touch events can be sensed on the above touch sensor panels by detectingchanges in the self-capacitance and/or mutual capacitance of the aboveconductive plates. In order to detect such changes, in some examples,the conductive plates can be coupled to sense circuitry using senseconnections. It can be beneficial for the resistances and/orcapacitances of these sense connections to be substantially uniformacross the touch screen so that transient operation of the senseconnections can be substantially uniform across the touch screen. Theexamples of the disclosure provide various techniques for balancing theresistances and/or capacitances of these sense connections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate an example mobile telephone, an example mediaplayer, an example personal computer and an example tablet computer thatcan each include an exemplary touch screen according to examples of thedisclosure.

FIG. 2 is a block diagram of an example computing system thatillustrates one implementation of an example touch screen according toexamples of the disclosure.

FIG. 3 illustrates an example configuration in which common electrodescan form portions of the touch sensing circuitry of a touch sensingsystem.

FIG. 4 illustrates an exemplary configuration for electricallyconnecting touch pixels in touch screen to sense channels according toexamples of the disclosure.

FIG. 5 illustrates an exemplary sense connection configuration accordingto examples of the disclosure.

FIG. 6 illustrates an exemplary sense connection configuration in whichthe resistances of the sense connections can be substantially equal.

FIG. 7 illustrates an exemplary sense connection configuration in whichthe resistances and the capacitances of the sense connections can besubstantially equal.

FIG. 8 illustrates another exemplary sense connection configuration inwhich the resistances and the capacitances of the sense connections canbe substantially equal.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

Some capacitive touch sensor panels can be formed by a matrix ofsubstantially transparent conductive plates made of materials such asIndium Tin Oxide (ITO), and some touch screens can be formed bypartially integrating touch sensing circuitry into a display pixelstackup (i.e., the stacked material layers forming the display pixels).Touch events can be sensed on the above touch sensor panels by detectingchanges in the self-capacitance and/or mutual capacitance of the aboveconductive plates. In order to detect such changes, in some examples,the conductive plates can be coupled to sense circuitry using senseconnections. It can be beneficial for the resistances and/orcapacitances of these sense connections to be substantially uniformacross the touch screen so that transient operation of the senseconnections can be substantially uniform across the touch screen. Theexamples of the disclosure provide various techniques for balancing theresistances and/or capacitances of these sense connections.

FIGS. 1A-1D show example systems in which a touch screen according toexamples of the disclosure may be implemented. FIG. 1A illustrates anexample mobile telephone 136 that includes a touch screen 124. FIG. 1Billustrates an example digital media player 140 that includes a touchscreen 126. FIG. 1C illustrates an example personal computer 144 thatincludes a touch screen 128. FIG. 1D illustrates an example tabletcomputer 148 that includes a touch screen 130. It is understood that theabove touch screens can be implemented in other devices as well,including in wearable devices.

In some examples, touch screens 124, 126, 128 and 130 can be based onself-capacitance. A self-capacitance based touch system can include amatrix of small plates of conductive material that can be referred to asa touch pixel or a touch pixel electrode. For example, a touch screencan include a plurality of touch pixels, each touch pixel correspondingto a particular location on the touch screen at which touch or proximity(i.e., a touch or proximity event) is to be sensed. Such a touch screencan be referred to as a pixelated self-capacitance touch screen. Duringoperation, the touch pixel can be stimulated with an AC waveform, andthe self-capacitance of the touch pixel can be measured. As an objectapproaches the touch pixel, the self-capacitance of the touch pixel canchange. This change in the self-capacitance of the touch pixel can bedetected and measured by the touch sensing system to determine thepositions of multiple objects when they touch, or come in proximity to,the touch screen. In some examples, the electrodes of a self-capacitancebased touch system can be formed from rows and columns of conductivematerial, and changes in the self-capacitance of the rows and columnscan be detected, similar to above.

In some examples, touch screens 124, 126, 128 and 130 can be based onmutual capacitance. A mutual capacitance based touch system can include,for example, drive regions and sense regions, such as drive lines andsense lines. For example, drive lines can be formed in rows while senselines can be formed in columns (e.g., orthogonal). Touch pixels can beformed at the intersections of the rows and columns During operation,the rows can be stimulated with an AC waveform and a mutual capacitancecan be formed between the row and the column of the touch pixel. As anobject approaches the touch pixel, some of the charge being coupledbetween the row and column of the touch pixel can instead be coupledonto the object. This reduction in charge coupling across the touchpixel can result in a net decrease in the mutual capacitance between therow and the column and a reduction in the AC waveform being coupledacross the touch pixel. This reduction in the charge-coupled AC waveformcan be detected and measured by the touch sensing system to determinethe positions of multiple objects when they touch the touch screen. Insome examples, a touch screen can be multi-touch, single touch,projection scan, full-imaging multi-touch, capacitive touch, etc.

FIG. 2 is a block diagram of an example computing system 200 thatillustrates one implementation of an example touch screen 220 accordingto examples of the disclosure. Computing system 200 can be included in,for example, mobile telephone 136, digital media player 140, personalcomputer 144, tablet computer 148, or any mobile or non-mobile computingdevice that includes a touch screen, including a wearable device.Computing system 200 can include a touch sensing system including one ormore touch processors 202, peripherals 204, a touch controller 206, andtouch sensing circuitry (described in more detail below). Peripherals204 can include, but are not limited to, random access memory (RAM) orother types of memory or storage, watchdog timers and the like. Touchcontroller 206 can include, but is not limited to, one or more sensechannels 208 and channel scan logic 210. Channel scan logic 210 canaccess RAM 212, autonomously read data from sense channels 208 andprovide control for the sense channels. In addition, channel scan logic210 can control sense channels 208 to generate stimulation signals atvarious frequencies and phases that can be selectively applied to thetouch pixels of touch screen 220, as described in more detail below. Insome examples, touch controller 206, touch processor 202 and peripherals204 can be integrated into a single application specific integratedcircuit (ASIC), and in some examples can be integrated with touch screen220 itself.

Touch screen 220 can be a self-capacitance touch screen, and can includetouch sensing circuitry that can include a capacitive sensing mediumhaving a plurality of touch pixels 222 (e.g., a pixelatedself-capacitance touch screen). It is understood that while touch screen220 is described herein as including touch pixels 222, the touch screencan additionally or alternatively include rows and columns of conductivematerial; the operation of such a touch screen would be similar to thatdescribed here. Additionally, it is understood that in some examples,touch screen 220 can be a mutual capacitance touch screen, as describedabove, though the description that follows will assume that the touchscreen is a self-capacitance touch screen having a plurality of touchpixel electrodes (“touch pixels”). Touch pixels 222 can be coupled tosense channels 208 in touch controller 206, can be driven by stimulationsignals from the sense channels through drive/sense interface 225, andcan be sensed by the sense channels through the drive/sense interface aswell, as described above. Labeling the conductive plates used to detecttouch (i.e., touch pixels 222) as “touch pixels” can be particularlyuseful when touch screen 220 is viewed as capturing an “image” of touch.In other words, after touch controller 206 has determined an amount oftouch detected at each touch pixel 222 in touch screen 220, the patternof touch pixels in the touch screen at which a touch occurred can bethought of as an “image” of touch (e.g., a pattern of fingers touchingthe touch screen).

Computing system 200 can also include a host processor 228 for receivingoutputs from touch processor 202 and performing actions based on theoutputs. For example, host processor 228 can be connected to programstorage 232 and a display controller, such as an LCD driver 234. The LCDdriver 234 can provide voltages on select (gate) lines to each pixeltransistor and can provide data signals along data lines to these sametransistors to control the pixel display image as described in moredetail below. Host processor 228 can use LCD driver 234 to generate animage on touch screen 220, such as an image of a user interface (UI),and can use touch processor 202 and touch controller 206 to detect atouch on or near touch screen 220. The touch input can be used bycomputer programs stored in program storage 232 to perform actions thatcan include, but are not limited to, moving an object such as a cursoror pointer, scrolling or panning, adjusting control settings, opening afile or document, viewing a menu, making a selection, executinginstructions, operating a peripheral device connected to the hostdevice, answering a telephone call, placing a telephone call,terminating a telephone call, changing the volume or audio settings,storing information related to telephone communications such asaddresses, frequently dialed numbers, received calls, missed calls,logging onto a computer or a computer network, permitting authorizedindividuals access to restricted areas of the computer or computernetwork, loading a user profile associated with a user's preferredarrangement of the computer desktop, permitting access to web content,launching a particular program, encrypting or decoding a message, and/orthe like. Host processor 228 can also perform additional functions thatmay not be related to touch processing.

Note that one or more of the functions described above, including theconfiguration of switches, can be performed by firmware stored in memory(e.g., one of the peripherals 204 in FIG. 2) and executed by touchprocessor 202, or stored in program storage 232 and executed by hostprocessor 228. The firmware can also be stored and/or transported withinany non-transitory computer-readable storage medium for use by or inconnection with an instruction execution system, apparatus, or device,such as a computer-based system, processor-containing system, or othersystem that can fetch the instructions from the instruction executionsystem, apparatus, or device and execute the instructions. In thecontext of this document, a “non-transitory computer-readable storagemedium” can be any medium (excluding signals) that can contain or storethe program for use by or in connection with the instruction executionsystem, apparatus, or device. The computer-readable storage medium caninclude, but is not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus or device,a portable computer diskette (magnetic), a random access memory (RAM)(magnetic), a read-only memory (ROM) (magnetic), an erasableprogrammable read-only memory (EPROM) (magnetic), a portable opticaldisc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory suchas compact flash cards, secured digital cards, USB memory devices,memory sticks, and the like.

The firmware can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “transport medium” can be any mediumthat can communicate, propagate or transport the program for use by orin connection with the instruction execution system, apparatus, ordevice. The transport medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic or infrared wired orwireless propagation medium.

In some examples, touch screen 220 can be an integrated touch screen inwhich touch sensing circuit elements of the touch sensing system can beintegrated into the display pixel stackups of a display. The circuitelements in touch screen 220 can include, for example, elements that canexist in LCD or other displays (e.g., OLED displays), such as one ormore pixel transistors (e.g., thin film transistors (TFTs)), gate lines,data lines, pixel electrodes and common electrodes. In any given displaypixel, a voltage between a pixel electrode and a common electrode cancontrol a luminance of the display pixel. The voltage on the pixelelectrode can be supplied by a data line through a pixel transistor,which can be controlled by a gate line. It is noted that circuitelements are not limited to whole circuit components, such as a wholecapacitor, a whole transistor, etc., but can include portions ofcircuitry, such as only one of the two plates of a parallel platecapacitor. FIG. 3 illustrates an example configuration in which commonelectrodes 302 can form portions of the touch sensing circuitry of atouch sensing system—in some examples of this disclosure, the commonelectrodes can form touch pixels used to detect an image of touch ontouch screen 300, as described above. Each common electrode 302 (i.e.,touch pixel) can include a plurality of display pixels 301, and eachdisplay pixel 301 can include a portion of a common electrode 302, whichcan be a circuit element of the display system circuitry in the displaypixel stackup (i.e., the stacked material layers forming the displaypixels) of the display pixels of some types of LCD or other displaysthat can operate as part of the display system to display an image.

In the example shown in FIG. 3, each common electrode 302 can serve as amulti-function circuit element that can operate as display circuitry ofthe display system of touch screen 300 and can also operate as touchsensing circuitry of the touch sensing system. In this example, eachcommon electrode 302 can operate as a common electrode of the displaycircuitry of the touch screen 300, as described above, and can alsooperate as touch sensing circuitry of the touch screen. For example, acommon electrode 302 can operate as a capacitive part of a touch pixelof the touch sensing circuitry during the touch sensing phase. Othercircuit elements of touch screen 300 can form part of the touch sensingcircuitry by, for example, switching electrical connections, etc. Morespecifically, in some examples, during the touch sensing phase, a gateline can be connected to a power supply, such as a charge pump, that canapply a voltage to maintain TFTs in display pixels included in a touchpixel in an “off” state. Stimulation signals can be applied to commonelectrode 302. Changes in the total self-capacitance of common electrode302 can be sensed through an operational amplifier, as previouslydiscussed. The change in the total self-capacitance of common electrode302 can depend on the proximity of a touch object, such as a finger, tothe common electrode. In this way, the measured change in totalself-capacitance of common electrode 302 can provide an indication oftouch on or near the touch screen.

In general, each of the touch sensing circuit elements may be either amulti-function circuit element that can form part of the touch sensingcircuitry and can perform one or more other functions, such as formingpart of the display circuitry, or may be a single-function circuitelement that can operate as touch sensing circuitry only. Similarly,each of the display circuit elements may be either a multi-functioncircuit element that can operate as display circuitry and perform one ormore other functions, such as operating as touch sensing circuitry, ormay be a single-function circuit element that can operate as displaycircuitry only. Therefore, in some examples, some of the circuitelements in the display pixel stackups can be multi-function circuitelements and other circuit elements may be single-function circuitelements. In other examples, all of the circuit elements of the displaypixel stackups may be single-function circuit elements.

In addition, although examples herein may describe the display circuitryas operating during a display phase, and describe the touch sensingcircuitry as operating during a touch sensing phase, it should beunderstood that a display phase and a touch sensing phase may beoperated at the same time, e.g., partially or completely overlap, or thedisplay phase and touch sensing phase may operate at different times.Also, although examples herein describe certain circuit elements asbeing multi-function and other circuit elements as beingsingle-function, it should be understood that the circuit elements arenot limited to the particular functionality in other examples. In otherwords, a circuit element that is described in one example herein as asingle-function circuit element may be configured as a multi-functioncircuit element in other examples, and vice versa.

The common electrodes 302 (i.e., touch pixels) and display pixels 301 ofFIG. 3 are shown as rectangular or square regions on touch screen 300.However, it is understood that the common electrodes 302 and displaypixels 301 are not limited to the shapes, orientations, and positionsshown, but can include any suitable configurations according to examplesof the disclosure.

As described above, the self-capacitance of each touch pixel (e.g.,touch pixel 222) in the touch screen of the disclosure can be sensed tocapture an image of touch across the touch screen. To allow for thesensing of the self-capacitance of individual touch pixels, it can benecessary to route one or more electrical connections between each ofthe touch pixels and the touch sensing circuitry (e.g., sense channels208) of the touch screen.

FIG. 4 illustrates an exemplary configuration for electricallyconnecting touch pixels 402 in touch screen 400 to sense channels 408according to examples of the disclosure. In some examples, sensechannels 408 can be located in a touch controller separate from thetouch screen, but in some examples, the sense channels can be located onthe touch screen. Touch screen 400 can include touch pixels 402, asdescribed above. Components of touch screen 400 other than touch pixels402 are not illustrated for ease of description. Each of touch pixels402 can be electrically connected to sense channels 408 through senseconnections 404 and connection points 406. In some examples, senseconnections 404 can connect touch pixels 402 to a location on the touchscreen (e.g., a flex circuit connection area) from which a separateconnection (e.g., a flex circuit) can complete the connection to sensechannels 408 (e.g., when the sense channels are located separate fromtouch screen 400). In some examples, sense connections 404 can connecttouch pixels 402 directly to sense channels 408 (e.g., when the sensechannels are located on touch screen 400). In some examples, connectionpoints 406 can be vias when sense connections 404 and touch pixels 402reside in different layers of touch screen 400 (e.g., when the senseconnections reside underneath the touch pixels, or when the senseconnections reside on top of the touch pixels); it is understood,however, that in some examples, the sense connections and the touchpixels can reside in the same layer of the touch screen, and theconnection points can represent a location where the sense connectionsand the touch pixels connect. As discussed above, in some examples,connection points 406 can allow for an electrical connection betweentouch pixels 402 and sense connections 404 through one or moreintervening layers that may exist between the touch pixels and the senseconnections in touch screen 400.

In connecting sense channels 408 and touch pixels 402, it can bebeneficial to balance the load (e.g., the resistance and/or thecapacitance) that each sense connection 404 presents to the sensechannels so that the transient operation of the sense connections can besubstantially uniform across touch screen 400 (e.g., an RC time constantfor each sense connection can be substantially the same). The examplesof the disclosure are directed to various techniques for achieving theabove load balancing.

Although the examples of the disclosure are presented in the context ofconnecting touch pixels to sense channels, it is understood that thetechniques described can be utilized in any context in which loadbalancing of connections between components can be desired (e.g.,connecting mutual capacitance drive lines to drive circuitry).

FIG. 5 illustrates an exemplary sense connection configuration 500according to examples of the disclosure. Touch pixels 502, 506, 510, 514and 518 can correspond to a column of touch pixels 402 on touch screen400 in FIG. 4, for example. Touch pixels 502, 506, 510, 514 and 518 areillustrated as being expanded in the horizontal dimension for ease ofillustration. Each touch pixel can be coupled to sense channels 501through respective connection points and sense connections—e.g., touchpixel 502 can be coupled to the sense channels through connection point503 and sense connection 504. The remaining touch pixels can besimilarly coupled to sense channels 501, as illustrated. Senseconnections 504, 508, 512, 516 and 520 can correspond to senseconnections 404, and connection points 503, 507, 511, 515 and 519 cancorrespond to connection points 406, for example.

The load (e.g., the resistance and/or the capacitance) presented by eachsense connection to sense channels 501 in the illustrated example willnow be described. As an initial matter, each sense connection in theillustrated example can have a different resistance, because, assumingeach sense connection is formed of the same material having the samewidth/depth, each sense connection can be required to travel differentdistances. For example, sense connection 504 can travel the longestdistance of the illustrated sense connections, because touch pixel 502can be the furthest touch pixel of the illustrated touch pixels fromsense channels 501. On the other hand, sense connection 520 can travelthe shortest distance because touch pixel 518 can be the closest touchpixel to sense channels 501. Thus, sense connection 504 can have thehighest resistance of the illustrated sense connections, senseconnection 520 can have the lowest resistance of the illustrated senseconnections, and the remaining sense connections can have resistancesbetween those of sense connection 504 and sense connection 520 based onthe respective traveling distance of each.

In contrast to the different resistances of the sense connections, thecapacitances presented by each sense connection to sense channels 501can be substantially balanced in the illustrated example. In thediscussions that follow, the capacitance presented by a sense connectionto sense channels 501 will be considered to include: 1) capacitancesresulting from overlap of the sense connection with touch pixels otherthan the touch pixel to which the sense connection is coupled, and 2)capacitances resulting from overlap of the touch pixel to which thesense connection is coupled with other sense connections. Capacitancesbetween sense connections can be relatively small, and thus notconsidered in this discussion, because the sense connections can bespaced relatively far apart from each other.

Considering first the capacitance presented by sense connection 504 tosense channels 501, the capacitance presented can be approximately 4C,where C can represent a capacitance resulting from the overlap of asense connection with a touch pixel. Specifically, sense connection 504can overlap touch pixels 506, 510, 514 and 518 before connecting totouch pixel 502 at connection point 503. Touch pixel 502, in theillustrated example, does not overlap with any sense connections, andthus may not contribute to the capacitance presented by sense connection504 to sense channels 501.

Sense connection 508 can also present a capacitance of approximately 4Cto sense channels 501. Specifically, sense connection 508 can overlapwith touch pixels 510, 514 and 518 before connecting to touch pixel 506at connection point 503, which can account for a capacitance ofapproximately 3C. Additionally, touch pixel 506, to which senseconnection 508 can be coupled, can overlap with sense connection 504,which can account for an additional capacitance of approximately 1C.Thus, the total capacitance presented by sense connection 508 to sensechannels 501 can be approximately 4C, which can be the same capacitancepresented by sense connection 504 to the sense channels. The totalcapacitances presented by the remaining sense connections to sensechannels 501 can similarly be approximately 4C.

Therefore, in the illustrated sense connection configuration 500, theresistance of each sense connection can be different, whereas thecapacitance presented by each sense connection to sense channels 501 canbe substantially the same. As discussed above, it can be beneficial toalso make the resistances of the sense connections substantially equal.

FIG. 6 illustrates an exemplary sense connection configuration 600 inwhich the resistances of the sense connections can be substantiallyequal. Sense connection configuration 600 can be similar to senseconnection configuration 500, except that the sense connections caninclude detour routing such that the total traveling length of eachsense connection can be substantially the same as the total travelinglength of the other sense connections. In this way, the total resistanceof each sense connection can be substantially the same as the totalresistance of the other sense connections.

Specifically, the resistance of sense connection 604 can be the targetresistance for the other sense connections to reach, because senseconnection 604 can necessarily be the longest sense connection as it canbe required to reach touch pixel 602 from sense channels 601. In otherwords, it can be the case that the resistance of sense connection 604cannot be substantially reduced by reducing the length of the senseconnection, as the length of the sense connection can be limited by thedistance of touch pixel 602 from sense channels 601. It is understoodthat while sense connection 604 is illustrated as including detourrouting similar to the other sense connections in sense connectionconfiguration 600, sense connection 604 need not include such detourrouting.

In order to substantially match the length (and thus the resistance) ofsense connection 604, the other sense connections can include detourrouting to make their total length substantially the same as the lengthof sense connection 604. For example, sense connection 608 can extendbeyond connection point 607 and turn back towards the connection pointat an appropriate location such that the total length of the senseconnection can be substantially the same as the total length of senseconnection 604. The remaining sense connections can similarly includesuch detour routing to make their lengths substantially the same as thelength of sense connection 604. As such, the resistances of the senseconnections can be made substantially equal. The illustrated detourrouting configuration is merely exemplary, and it is understood thatother routing configurations in which the lengths of the senseconnections are substantially equalized are within the scope of thedisclosure. Further, in some examples, instead of adjusting senseconnection length, other characteristics of the sense connections (e.g.,widths, thicknesses, materials, and/or any other characteristics) can beadjusted to achieve the goals of balancing the resistances and/or thecapacitances associated with the sense connections—however, for ease ofdescription, the examples of the disclosure will focus on load balancingtechniques for sense connections made of the same material, having thesame width, etc.

Balancing the resistances of the sense connections in sense connectionconfiguration 600 as described above can cause the capacitancespresented by those sense connections to sense channels 601 to becomeunbalanced. For example, the capacitance presented by sense connection612 to sense channels 601 can be a combination of: 1) 4C, as before, 2)an additional capacitance resulting from the overlap of the detourrouting of the sense connection with touch pixel 606, and 3) anadditional capacitance resulting from the overlap of the detour routingof sense connection 616 with touch pixel 610. In contrast, thecapacitance presented by sense connection 604 to sense channels 601 canremain at 4C, as before. Such differences in capacitances resulting fromdetour routing-touch pixel overlap can similarly exist in the remainingsense connections. Therefore, while the resistances of the senseconnections in sense connection configuration 600 can be substantiallybalanced, the capacitances that the sense connections present to sensechannels 601 can be unbalanced.

FIG. 7 illustrates an exemplary sense connection configuration 700 inwhich the resistances and the capacitances of the sense connections canbe substantially equal. Sense connection configuration 700 can besimilar to sense connection configuration 600, except that the senseconnections can be electrically coupled to dummy routing, illustrated asdashed lines, such that the total sense connection-touch pixel overlapfor each sense connection can be substantially the same as the totalsense connection-touch pixel overlap for other sense connections.Additionally, because the sense connections can include the same detourrouting as in sense connection configuration 600, and because the endsof the dummy routing can be open-circuited (i.e., configured in such away as to prevent current from flowing through the dummy routing), theresistances of the sense connections can also be substantially equal.

For example, sense connection 704 can have the same resistance as senseconnection 604. While sense connection 704 can include dummy routing 705that can be electrically connected to the sense connection at connectionpoint 703, substantially no current may flow through the dummy routingbecause the end of the dummy routing can be open-circuited. Thus, theresistance of sense connection 704 from sense channels 701 to touchpixel 702 can be substantially the same as the resistance of senseconnection 604. This can be true for the remaining sense connections insense connection configuration 700 as well. Thus, the resistances of thesense connections can be substantially equal, as above.

The capacitance that sense connection 704 can present to sense channels701 can, however, differ from the capacitance that sense connection 604can present to sense channels 601. In particular, the capacitancepresented by sense connection 704 to sense channels 701 can beapproximately 16C-4C resulting from sense connection-touch pixel overlap(overlap with touch pixels 706, 710, 714 and 718), 4C resulting fromdummy routing 705-touch pixel overlap (overlap with touch pixels 706,710, 714 and 718), and 8C resulting from overlap of the dummy routingfor each of the other sense connections with touch pixel 702.

The capacitance that sense connection 708 can present to sense channels701 can also be approximately 16C-3C resulting from senseconnection-touch pixel overlap (overlap with touch pixels 710, 714 and718), 5C resulting from dummy routing 709-touch pixel overlap (overlapwith touch pixels 702, 710, 714 and 718), and 8C resulting from overlapof each of the other sense connections and/or their associated dummyrouting with touch pixel 706. The capacitances that the remaining senseconnections can present to sense channels 701 can similarly beapproximately 16C.

Therefore, in the illustrated sense connection configuration 700, theresistance of each sense connection can be substantially the same, andthe capacitance presented by each sense connection to sense channels 701can also be substantially the same. As such, the RC time constants ofthe sense connections can be substantially uniform across the touchscreen. The illustrated dummy routing configuration is merely exemplary,and it is understood that other dummy routing configurations in whichthe sense connection-touch pixel overlaps of the sense connections aresubstantially equalized are within the scope of the disclosure.

FIG. 8 illustrates another exemplary sense connection configuration 800in which the resistances and the capacitances of the sense connectionscan be substantially equal. The sense connections in sense connectionconfiguration 800 can be electrically coupled to extra lines (e.g.,dummy routing) to equalize the capacitances of the sense connections,similar to the dummy routing in sense connection configuration 700.However, the sense connections in sense connection configuration 800 canutilize some of the extra lines that are used to equalize capacitancesto also reduce the resistances of the sense connections in asubstantially equal manner across the touch screen. Thus, thecapacitances and the resistances of the sense connections can remainsubstantially balanced, while the absolute values of the resistances ofthe sense connections can be reduced.

In the illustrated example, the capacitance presented by each senseconnection to sense channels 801 can be approximately 24C, for reasonssimilar to those described previously. The details are omitted here forbrevity. Therefore, the capacitances presented by each sense connectionto sense channels 801 can be substantially the same.

The resistance of sense connection 804 can be substantially less thanthe resistance of sense connection 704, because sense connection 804 canutilize: 1) three lines to carry one or more signals to a locationslightly before connection point 803, 2) two lines to carry the one ormore signals through part of the detour routing associated with senseconnection 804, and 3) one line to carry the one or more signals theremaining distance to the connection point and touch pixel 802. Senseconnection 704, on the other hand, can utilize only a single line tocarry the one or more signals to connection point 703 and touch pixel702. Therefore, the resistance of sense connection 804 can besubstantially less than the resistance of sense connection 704—in someexamples, anywhere from 30% to 70% less.

The length and configuration of the detour routing for each senseconnection can be set to ensure that the total resistances of the senseconnections are substantially the same, similar to as described abovewith respect to FIG. 6. In the illustrated example, this can beaccomplished by adjusting the length of the double-line and single-lineportions of the detour routing.

As such, in the illustrated sense connection configuration 800, theresistance of each sense connection can be substantially the same, andthe capacitance presented by each sense connection to sense channels 801can also be substantially the same. Additionally, the absolute values ofthe resistances of the sense connections can be reduced as compared withthe sense connections in FIGS. 5-7, which, in some examples, can offsetany increase in sense connection capacitance that may result fromincreased overlaps between sense connections/dummy routing and touchpixels due to the use of extra lines. As a result, the RC time constantsassociated with the sense connections can be reduced while alsosubstantially maintaining the uniformity of the RC time constants acrossthe touch screen. The illustrated sense connection routing configuration(sense connection and detour routing) is merely exemplary, and it isunderstood that other routing configurations in which the resistances ofthe sense connections are reduced and substantially equalized are withinthe scope of the disclosure. The illustrated dummy routing configurationis also merely exemplary, and it is understood that other dummy routingconfigurations in which the sense connection capacitances aresubstantially equalized are also within the scope of the disclosure.

Thus, the examples of the disclosure provide one or more configurationsfor balancing and/or reducing the resistive and/or capacitive load seenby drive and/or sense circuitry in a touch screen.

Therefore, according to the above, some examples of the disclosure aredirected to a touch screen comprising a first element of a plurality ofelements, the first element coupled to a first sense connection; and asecond element of the plurality of elements, the second element coupledto a second sense connection, wherein the first and second senseconnections are configured such that a load presented by the first senseconnection and the first element is substantially equal to a loadpresented by the second sense connection and the second element.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the touch screen comprises a self-capacitancetouch screen, and the first and second elements comprise distinct touchpixel electrodes of the self-capacitance touch screen. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the first sense connection and the second sense connection areconfigured to couple the first element and the second element,respectively, to a location on the touch screen, and the first elementis disposed a first distance from the location on the touch screen, andthe second element is disposed a second distance from the location onthe touch screen, the first distance being different than the seconddistance. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the location comprises a flex circuitconnection area. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the location comprises sensechannels. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the first sense connection comprisesa first detour routing, the second sense connection comprises a seconddetour routing, and the first detour routing and the second detourrouting are configured such that a resistance of the first senseconnection is substantially equal to a resistance of the second senseconnection. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, a total length of the first senseconnection including the first detour routing substantially equals atotal length of the second sense connection including the second detourrouting. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the touch screen further comprisesfirst dummy routing coupled to the first sense connection; and seconddummy routing coupled to the second sense connection, wherein the firstdummy routing and the second dummy routing are configured such that afirst capacitance presented by the first sense connection issubstantially equal to a second capacitance presented by the secondsense connection. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first and secondcapacitances each include a capacitance between the first senseconnection and the second element, a capacitance between the first dummyrouting and the second element, a capacitance between the second senseconnection and the first element, and a capacitance between the seconddummy routing and the first element. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the firstelement overlaps with the second sense connection a first number oftimes, the first element overlaps with the second dummy routing a secondnumber of times, the second element overlaps with the first senseconnection a third number of times, the second element overlaps with thefirst dummy routing a fourth number of times, and a sum of the first andsecond numbers equals a sum of the third and fourth numbers.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first dummy routing is configured so as tonot alter a first resistance of the first sense connection, and thesecond dummy routing is configured so as to not alter a secondresistance of the second sense connection. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, thefirst sense connection comprises a first portion and a second portion,the first portion including a first number of lines, and the secondportion including a second number of lines, different from the firstnumber of lines, and the second sense connection comprises a thirdportion and a fourth portion, the third portion including a third numberof lines, and the fourth portion including a fourth number of lines,different from the third number of lines. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, thefirst number equals the third number, and the second number equals thefourth number.

Some examples of the disclosure are directed to a method for fabricatinga touch screen, the method comprising forming a first element of aplurality of elements; forming a first sense connection coupled to thefirst element; forming a second element of the plurality of elements;and forming a second sense connection coupled to the second element,wherein the first and second sense connections are configured such thata load presented by the first sense connection and the first element issubstantially equal to a load presented by the second sense connectionand the second element. Additionally or alternatively to one or more ofthe examples disclosed above, in some examples, the touch screencomprises a self-capacitance touch screen, and the first and secondelements comprise distinct touch pixel electrodes of theself-capacitance touch screen. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, the first senseconnection and the second sense connection are configured to couple thefirst element and the second element, respectively, to a location on thetouch screen, and forming the first element comprises forming the firstelement disposed a first distance from the location on the touch screen,and forming the second element comprises forming the second elementdisposed a second distance from the location on the touch screen, thefirst distance being different than the second distance. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the location comprises a flex circuit connection area.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, forming the first sense connection comprisesforming the first sense connection including a first detour routing,forming the second sense connection comprises forming the second senseconnection including a second detour routing, and the first detourrouting and the second detour routing are configured such that aresistance of the first sense connection is substantially equal to aresistance of the second sense connection. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, atotal length of the first sense connection including the first detourrouting substantially equals a total length of the second senseconnection including the second detour routing. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the method further comprises forming first dummy routingcoupled to the first sense connection; and forming second dummy routingcoupled to the second sense connection, wherein the first dummy routingand the second dummy routing are configured such that a firstcapacitance presented by the first sense connection is substantiallyequal to a second capacitance presented by the second sense connection.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first and second capacitances each includea capacitance between the first sense connection and the second element,a capacitance between the first dummy routing and the second element, acapacitance between the second sense connection and the first element,and a capacitance between the second dummy routing and the firstelement. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the first element overlaps with thesecond sense connection a first number of times, the first elementoverlaps with the second dummy routing a second number of times, thesecond element overlaps with the first sense connection a third numberof times, the second element overlaps with the first dummy routing afourth number of times, and a sum of the first and second numbers equalsa sum of the third and fourth numbers. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the firstdummy routing is configured so as to not alter a first resistance of thefirst sense connection, and the second dummy routing is configured so asto not alter a second resistance of the second sense connection.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, forming the first sense connection comprisesforming the first sense connection including a first portion and asecond portion, the first portion including a first number of lines, andthe second portion including a second number of lines, different fromthe first number of lines, and forming the second sense connectioncomprises forming the second sense connection including a third portionand a fourth portion, the third portion including a third number oflines, and the fourth portion including a fourth number of lines,different from the third number of lines. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, thefirst number equals the third number, and the second number equals thefourth number.

Although examples of this disclosure have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of examples of this disclosure as defined bythe appended claims.

The invention claimed is:
 1. A touch screen comprising: a first elementof a plurality of elements, the first element coupled to a first senseconnection; a second element of the plurality of elements, the secondelement coupled to a second sense connection; first dummy routingcoupled to the first sense connection, the first dummy routingoverlapping one or more elements of the plurality of elements; andsecond dummy routing coupled to the second sense connection, wherein thefirst and second sense connections and the first dummy routing areconfigured such that a load presented by the first sense connection andthe first element is substantially equal to a load presented by thesecond sense connection and the second element, and the first dummyrouting and the second dummy routing are configured such that a firstcapacitance presented by the first sense connection is substantiallyequal to a second capacitance presented by the second sense connection.2. The touch screen of claim 1, wherein: the touch screen comprises aself-capacitance touch screen, and the first and second elementscomprise distinct touch pixel electrodes of the self-capacitance touchscreen.
 3. The touch screen of claim 1, wherein: the first senseconnection and the second sense connection are configured to couple thefirst element and the second element, respectively, to a location on thetouch screen, and the first element is disposed a first distance fromthe location on the touch screen, and the second element is disposed asecond distance from the location on the touch screen, the firstdistance being different than the second distance.
 4. The touch screenof claim 3, wherein the location comprises a flex circuit connectionarea.
 5. The touch screen of claim 3, wherein the location comprisessense channels.
 6. The touch screen of claim 1, wherein: the first senseconnection comprises a first detour routing, the second sense connectioncomprises a second detour routing, and the first detour routing and thesecond detour routing are configured such that a resistance of the firstsense connection is substantially equal to a resistance of the secondsense connection.
 7. The touch screen of claim 6, wherein a total lengthof the first sense connection including the first detour routingsubstantially equals a total length of the second sense connectionincluding the second detour routing.
 8. The touch screen of claim 1,wherein the first and second capacitances each include: a capacitancebetween the first sense connection and the second element, a capacitancebetween the first dummy routing and the second element, a capacitancebetween the second sense connection and the first element, and acapacitance between the second dummy routing and the first element. 9.The touch screen of claim 1, wherein: the first element overlaps withthe second sense connection a first number of times, the first elementoverlaps with the second dummy routing a second number of times, thesecond element overlaps with the first sense connection a third numberof times, the second element overlaps with the first dummy routing afourth number of times, and a sum of the first and second numbers equalsa sum of the third and fourth numbers.
 10. The touch screen of claim 1,wherein the first dummy routing is configured so as to not alter a firstresistance of the first sense connection, and the second dummy routingis configured so as to not alter a second resistance of the second senseconnection.
 11. The touch screen of claim 1, wherein: the first senseconnection comprises a first portion and a second portion, the firstportion including a first number of lines, and the second portionincluding a second number of lines, different from the first number oflines, and the second sense connection comprises a third portion and afourth portion, the third portion including a third number of lines, andthe fourth portion including a fourth number of lines, different fromthe third number of lines.
 12. The touch screen of claim 11, wherein:the first number equals the third number, and the second number equalsthe fourth number.
 13. A method for fabricating a touch screen, themethod comprising: forming a first element of a plurality of elements;forming a first sense connection coupled to the first element; forming asecond element of the plurality of elements; forming a second senseconnection coupled to the second element; forming a first dummy routingcoupled to the first sense connection, the first dummy routingoverlapping one or more elements of the plurality of elements; andforming second dummy routing coupled to the second sense connection,wherein the first and second sense connections and the first dummyrouting are configured such that a load presented by the first senseconnection and the first element is substantially equal to a loadpresented by the second sense connection and the second element, and thefirst dummy routing and the second dummy routing are configured suchthat a first capacitance presented by the first sense connection issubstantially equal to a second capacitance presented by the secondsense connection.
 14. The method of claim 13, wherein: the touch screencomprises a self-capacitance touch screen, and the first and secondelements comprise distinct touch pixel electrodes of theself-capacitance touch screen.
 15. The method of claim 13, wherein: thefirst sense connection and the second sense connection are configured tocouple the first element and the second element, respectively, to alocation on the touch screen, and forming the first element comprisesforming the first element disposed a first distance from the location onthe touch screen, and forming the second element comprises forming thesecond element disposed a second distance from the location on the touchscreen, the first distance being different than the second distance. 16.The method of claim 15, wherein the location comprises a flex circuitconnection area.
 17. The method of claim 13, wherein: forming the firstsense connection comprises forming the first sense connection includinga first detour routing, forming the second sense connection comprisesforming the second sense connection including a second detour routing,and the first detour routing and the second detour routing areconfigured such that a resistance of the first sense connection issubstantially equal to a resistance of the second sense connection. 18.The method of claim 17, wherein a total length of the first senseconnection including the first detour routing substantially equals atotal length of the second sense connection including the second detourrouting.
 19. The method of claim 13, wherein the first and secondcapacitances each include: a capacitance between the first senseconnection and the second element, a capacitance between the first dummyrouting and the second element, a capacitance between the second senseconnection and the first element, and a capacitance between the seconddummy routing and the first element.
 20. The method of claim 13,wherein: the first element overlaps with the second sense connection afirst number of times, the first element overlaps with the second dummyrouting a second number of times, the second element overlaps with thefirst sense connection a third number of times, the second elementoverlaps with the first dummy routing a fourth number of times, and asum of the first and second numbers equals a sum of the third and fourthnumbers.
 21. The method of claim 13, wherein the first dummy routing isconfigured so as to not alter a first resistance of the first senseconnection, and the second dummy routing is configured so as to notalter a second resistance of the second sense connection.
 22. The methodof claim 13, wherein: forming the first sense connection comprisesforming the first sense connection including a first portion and asecond portion, the first portion including a first number of lines, andthe second portion including a second number of lines, different fromthe first number of lines, and forming the second sense connectioncomprises forming the second sense connection including a third portionand a fourth portion, the third portion including a third number oflines, and the fourth portion including a fourth number of lines,different from the third number of lines.
 23. The method of claim 22,wherein: the first number equals the third number, and the second numberequals the fourth number.
 24. The touch screen of claim 1, wherein: thefirst sense connection is disposed along a first axis on the touchscreen between a first location and a second location, the first senseconnection is coupled to sense circuitry at the first location, thefirst dummy routing is coupled to the first sense connection at thesecond location, and the first dummy routing is disposed along the firstaxis.
 25. The touch screen of claim 1, wherein: the first senseconnection comprises a first conductive trace pattern, and the firstdummy routing comprises a second conductive trace pattern, correspondingto the first conductive trace pattern.
 26. The touch screen of claim 25,wherein: the first sense connection comprises a first number of parallelfirst conductive traces, and the first dummy routing comprises the firstnumber of parallel second conductive traces.
 27. The touch screen ofclaim 1, wherein: the first and second sense connections and the firstdummy routing are configured such that a resistive and capacitive loadpresented by the first sense connection and the first element issubstantially equal to a resistive and capacitive load presented by thesecond sense connection and the second element.
 28. The touch screen ofclaim 10, wherein: the first sense connection is configured to conduct aDC electrical current, and the first dummy routing is configured not toconduct a DC electrical current.
 29. The method of claim 13, wherein thefirst sense connection is disposed along a first axis on the touchscreen between a first location and a second location, the first senseconnection is coupled to sense circuitry at the first location, thefirst dummy routing is coupled to the first sense connection at thesecond location, and the first dummy routing is disposed along the firstaxis.
 30. The method of claim 13, wherein the first sense connectioncomprises a first conductive trace pattern, and the first dummy routingcomprises a second conductive trace pattern, corresponding to the firstconductive trace pattern.
 31. The method of claim 30, wherein the firstsense connection comprises a first number of parallel first conductivetraces, and the first dummy routing comprises the first number ofparallel second conductive traces.
 32. The method of claim 13, wherein:the first and second sense connections are configured such that aresistive and capacitive load presented by the first sense connectionand the first element is substantially equal to a resistive andcapacitive load presented by the second sense connection and the secondelement.
 33. The method of claim 21, wherein: the first sense connectionis configured to conduct a DC electrical current; and the first dummyrouting is configured not to conduct a DC electrical current.